1. Field of the Invention
This invention relates to a traveller and support for a safety line. The traveller can be used to secure fall safety equipment to a safety line which is supported by the supports and the traveller and supports cooperate to allow the traveller to move along the safety line and traverse the supports without the traveller being detached from the safety line.
2. Background Art
In order to protect personnel from falls when working at height it is usual, and often a legal requirement, to provide an elongate safety line or track running across or along the area in which the personnel are to work and to attach the personnel to the elongate safety line using a traveller able to slide along the line and connected to a safety harness worn by the personnel through a flexible lanyard.
The flexible lanyard allows the user freedom of movement to either side of the safety line and the traveller is pulled along the safety line by the lanyard to follow the user as they move along the safety line.
The safety line is anchored at each end. Further, in order to allow a long uninterrupted safety line and to allow the safety line to be guided around corners it is usually necessary for the safety line to also be mounted on a number of intermediate supports disposed along its length. Accordingly, the traveller and supports are arranged to cooperate so that the traveller can automatically pass along the safety line over the intermediate supports when pulled by the user with the lanyard without it being necessary to detach the traveller from the safety line.
A number of systems have been proposed in which this is carried out by the intermediate support including an arm section narrower than the safety line and the traveller being formed in a substantially C-shape broken by a slot, the slot being narrower than the safety line but wider than the arm of the intermediate support so that arm can pass through the slot to allow the traveller to traverse the intermediate support when pulled along the safety line but not allowing the traveller to become detached from the safety line.
A problem which has been encountered in systems of this type is ensuring that the slot in the traveller is properly aligned with the arm of the intermediate support in order to allow passage of the traveller over the intermediate support.
It has been proposed to overcome this problem in the past by using two parallel safety lines or a track having a non-circular cross-section so that a traveller engaged with both parallel safety lines or with the track respectively has its orientation controlled so that the slot and support are in alignment. However such an approach cannot be used in a traveller for use with a single safety line because a safety line has a substantially circular cross-section and so cannot be used to control the orientation of a traveller sliding along it.
It has also been proposed to control the alignment of a traveller on a single safety line so that the slot aligns with the safety line arm by using the load applied to the traveller by the safety lanyard to control the orientation of the traveller.
The problem with systems of this type is that in order for the traveller to be correctly rotationally aligned on the safety line so that the slot is aligned with the intermediate support arm the load applied by the safety lanyard to the traveller must be maintained within a small specified range of directions.
For example, where the safety line passes over the area in which users are to work above their head height the traveller and intermediate supports can be arranged so that the slot in the traveller is aligned with the intermediate support arm when the load applied to the traveller through the safety lanyard is vertically below, or in a small arc centered on the vertical below, the safety line. However, such a system suffers from the problem that it will not work if the user moves out of a narrow strip centered below the safety line because this will result in off vertical loads being applied through the lanyard as the user moves further away from the safety line. This will cause the traveller to rotate until the traveller slot and intermediate support arm no longer align. Accordingly, systems of this type are only suitable for use in situations where personnel movement is constrained to a narrow strip below the safety line, such as movement along catwalks, but are not suitable for situations where personnel can move freely about a large area.
Similar arrangements have also been proposed for use on roofs where the safety line is mounted a short distance above the roof surface on which the personnel can walk. Again, the usefulness of systems of this type is limited by the problem that the orientation of the load applied through the safety lanyard must be within a narrow range to maintain the alignment of the traveller slot with the intermediate safety arm. As a result, such systems are “handed” in that the user must always remain on the same side of the safety line and the distance which the user can move from the safety line is relatively small because if the user moves too far from the safety line the orientation of the force applied to the traveller by the safety lanyard cannot be reliably kept within an acceptable range for orientation of the arm and slot.